Systems and methods for checking status of a pressure transducer

ABSTRACT

A method of controlling a gas furnace system includes controlling a motor of a draft inducer coupled to a conduit to increase a speed of the motor from a stopped condition in response to a call for heat, and receiving pressure signals output by a pressure transducer responsive to pressure in the conduit. Signals indicating whether a pressure switch responsive to pressure in the conduit is in a first state or a second state are received. A first status of the pressure transducer is determined based on the received pressure signals from the pressure transducer and the signals indicating whether the pressure switch is in the first state or the second state. The method includes continuing to operate the motor when the first status does not indicate that the pressure transducer is unreliable, and stopping the motor when the first status indicates that the pressure transducer is unreliable.

FIELD

The field of the disclosure relates systems including a pressuretransducer, and more particularly, to systems and methods for checkingthe status of a pressure transducer in an HVAC system.

BACKGROUND

Pressure switches are commonly used in HVAC systems to monitor when apressure exceeds or drops below a predetermined threshold pressure. Suchpressure switches are reliable technology, but only provide a limitedamount of data. A pressure transducer may be used to monitor the inducerpressure in an HVAC system, especially to achieve low NOx emission. Apressure transducer outputs a voltage that is proportional (whetherdirectly proportional or inversely proportional) to the pressure itsenses from a hose in a conduit that connects to the sensor. The use ofpressure transducers in HVAC systems is less established than pressureswitches, and the reliability and accuracy of the pressure transducersis less established. As with all components, the pressure transducer mayfail under certain conditions like humidity, dust, vibration, shock,overvoltage, etc. One failure mode observed results in the output of thepressure transducer being at a constant voltage instead of a value thatvaries according to the input pressure. Also, apparent pressuretransducer failures may be the result of improper connections, such asthe pressure transducer's ground pin not being connected properly in theadapter harness that goes from the pressure transducer to the controlboard. When the pressure transducer fails, it can negatively affect theproduct performance, potentially including making audible noise orgenerating CO. Because of this, it is desired to detect failures fromthese types of pressure transducers, notify a user of the status of thetransducer, and/or prevent or stop operation when the pressuretransducer has failed.

This Background section is intended to introduce the reader to variousaspects of art that may be related to various aspects of the presentdisclosure, which are described and/or claimed below. This discussion isbelieved to be helpful in providing the reader with backgroundinformation to facilitate a better understanding of the various aspectsof the present disclosure. Accordingly, it should be understood thatthese statements are to be read in this light, and not as admissions ofprior art.

SUMMARY

In one aspect, a gas furnace system includes a draft inducer, a pressuretransducer, a pressure switch and a controller. The draft inducerincludes a motor and is in fluid communication with a conduit. Thepressure transducer is positioned to sense a pressure within the conduitand output signals proportional to the sensed pressure. The pressureswitch is connected to the controller and positioned to sense thepressure within the conduit. The pressure switch has a first state and asecond state, and is configured to be in the first state when the sensedpressure is below a predetermined pressure and to switch to the secondstate when the sensed pressure reaches or exceeds the predeterminedpressure. The controller is connected to the draft inducer, the pressuretransducer, and the pressure switch. The controller includes a processorprogrammed to receive pressure signals output by the pressuretransducer, receive signals indicating whether the pressure switch is inthe first state or the second state, control the motor of the draftinducer in response to a call for heat, and determine a first status ofthe pressure transducer based at least in part on the received pressuresignals from the pressure transducer and the signals indicating whetherthe pressure switch is in the first state or the second state.

Another aspect is a controller for a gas furnace system including adraft inducer having a motor, a pressure transducer positioned to sensea pressure within a conduit and output signals proportional to thesensed pressure, and a pressure switch positioned to sense the pressurewithin the conduit. The pressure switch has a first state and a secondstate, and is configured to be in the first state when the sensedpressure is below a predetermined pressure and to switch to the secondstate when the sensed pressure reaches or exceeds the predeterminedpressure. The controller includes a processor programmed to receivepressure signals output by the pressure transducer, receive signalsindicating whether the pressure switch is in the first state or thesecond state, control the motor of the draft inducer in response to acall for heat, and determine a first status of the pressure transducerbased at least in part on the received pressure signals from thepressure transducer and the signals indicating whether the pressureswitch is in the first state or the second state.

Another aspect is a method of controlling a gas furnace system. Themethod includes controlling a motor of a draft inducer coupled to aconduit to increase a speed of the motor from a stopped condition inresponse to a call for heat, and receiving pressure signals output by apressure transducer responsive to pressure in the conduit. Signalsindicating whether a pressure switch responsive to pressure in theconduit is in a first state or a second state are received. A firststatus of the pressure transducer is determined based at least in parton the received pressure signals from the pressure transducer and thesignals indicating whether the pressure switch is in the first state orthe second state. The method includes continuing to operate the motorwhen the first status does not indicate that the pressure transducer isunreliable, and stopping the motor when the first status indicates thatthe pressure transducer is unreliable.

Various refinements exist of the features noted in relation to theabove-mentioned aspects. Further features may also be incorporated inthe above-mentioned aspects as well. These refinements and additionalfeatures may exist individually or in any combination. For instance,various features discussed below in relation to any of the illustratedembodiments may be incorporated into any of the above-described aspects,alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a gas furnace system including afurnace control system.

FIG. 2 is a block diagram of the furnace controller of FIG. 1 andcomponent connections of the gas furnace system of FIG. 1.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

For conciseness, examples will be described with respect to a gaspowered furnace. However, the methods and systems described herein maybe applied to any suitable system or appliance including a pressurecontrolled or influenced by another controlled component.

Referring initially to FIG. 1, a gas furnace system of one embodimentfor heating a temperature controlled environment is indicated generallyat 100. The gas furnace system 100 generally includes a combustionchamber 102 for generating heat from combustible gases, a heat exchanger104, and an air circulator 106 for circulating fluid (e.g., air) pastthe heat exchanger 104 to transfer heat generated by the combustionchamber 102 to the circulating fluid.

The combustion chamber 102 includes a burner assembly 108 connected to agas fuel supply (not shown) via a gas inlet 110, and an ignition device112, such as a hot surface ignitor, a spark ignitor, an intermittentpilot, or the like configured to ignite an air/fuel mixture within thecombustion chamber 102. The burner assembly 108 includes one or moreburners through which fuel gas is fed. The supply of fuel gas to theburner assembly 108 is controlled by a gas valve assembly 114, which, inthe illustrated embodiment, includes a main burner valve 116 and asafety valve 118. In embodiments in which the ignition device 112 is anintermittent pilot, a supply of fuel gas to the intermittent pilot iscontrolled by a pilot gas valve (not shown).

An inducer blower 120 (also referred to as a draft inducer) is connectedto the combustion chamber 102 by a blower inlet 122. The inducer blower120 is configured to draw fresh (i.e., uncombusted) air into thecombustion chamber 102 through an air inlet 124 to mix fuel gas with airto provide a combustible air/fuel mixture. The inducer blower 120 isalso configured to force exhaust gases out of the combustion chamber 102and vent the exhaust gases to atmosphere through an exhaust outlet 126.The inducer blower 120 includes a motor (not shown), that drives a fan,impeller, or the like to move air.

The combustion chamber 102 is fluidly connected to the heat exchanger104. Combusted gases from the combustion chamber 102 are circulatedthrough the heat exchanger 104 while the air circulator 106 forces airfrom the temperature controlled environment into contact with the heatexchanger 104 to exchange heat between the heat exchanger 104 and thetemperature controlled environment. The air circulator 106 subsequentlyforces the air through an outlet 138 and back into the temperaturecontrolled environment.

The operation of the system 100 is generally controlled by a furnacecontrol system 139, which includes a safety system 140, a fan control142, a processor 141, a memory 143, a spark ignition controller 145, anda thermostat 128 connected to the furnace control system 139. Otherembodiments may use hot surface ignition or a pilot rather than directspark ignition using a spark ignition controller. The thermostat 128 isconnected to one or more temperature sensors (not shown) for measuringthe temperature of the temperature controlled environment. The furnacecontrol system 139 is connected to each of the gas valve assembly 114,the ignition device 112, the inducer blower 120, and the air circulator106 for controlling operation of the components in response to controlsignals received from the thermostat 128. Generally, the fan control 142controls operation of the air circulator 106 and inducer blower 120, andthe safety system 140 monitors and protects against safety failures(such as failure of ignition during an attempt to light gas at theburner assembly 108). The spark ignition controller 145 controls themain gas valve, the pilot gas valve (if applicable), and the ignitiondevice 112 to ignite gas at the burner assembly 108 when desired. Thespark ignition controller 145 is also communicatively connected to aflame sensor 136 (shown in FIG. 2) that detects whether or not a flamehas been ignited on the burner assembly 108 and/or on an intermittentpilot (where applicable). Moreover, in some embodiments, one or both ofthe safety system 140 and the fan control 142 are integrated with thespark ignition controller 145. In still other embodiments, the sparkignition controller 145 functions are performed by the furnace controlsystem 139 without a separate spark ignition controller 145. A mobiledevice 144, such as a mobile phone, a tablet computing device, a laptopcomputing device, a smart watch, or the like, may be used for wirelesscommunication with the furnace control system 139 and/or the sparkignition controller 145. Other embodiments are not configured forcommunication with a mobile device 144.

The processor 141 is configured for executing instructions to cause thefurnace control system 139 to perform as described herein. In someembodiments, executable instructions are stored in the memory 143. Theprocessor 141 may include one or more processing units (e.g., in amulti-core configuration). The memory 143 is any device allowinginformation such as executable instructions and/or other data to bestored and retrieved. The memory 143 may include one or morecomputer-readable media. The memory 143 stores computer-readableinstructions for control of the system 100 as described herein. The termprocessor, as used herein, refers to central processing units,microprocessors, microcontrollers, reduced instruction set circuits(RISC), application specific integrated circuits (ASIC), logic circuits,and any other circuit or processor capable of executing the functionsdescribed herein. The above are examples only, and are thus not intendedto limit in any way the definition and/or meaning of the term“processor.” The memory may include, but is not limited to, randomaccess memory (RAM) such as dynamic RAM (DRAM) or static RAM (SRAM),read-only memory (ROM), erasable programmable read-only memory (EPROM),electrically erasable programmable read-only memory (EEPROM), andnon-volatile RAM (NVRAM). The above memory types are example only, andare thus not limiting as to the types of memory usable for storage ofdata, instructions, and/or a computer program.

With additional reference to FIG. 2, the system 100 includes a pluralityof sensors and detectors for monitoring the environmental and operatingconditions of the system 100. The illustrated furnace system includes apressure transducer 129, a pressure switch 130, a temperature sensor132, a flame rollout detector 134, and a flame sensor 136. The furnacecontrol system 139 is connected to each of the pressure transducer 129,the pressure switch 130, the temperature sensor 132, the flame rolloutdetector 134, and the flame sensor 136, and is configured to control thefurnace system 100 based on signals received from the sensors anddetectors. Other embodiments do not include the pressure switch 130, andinclude only the pressure transducer 129.

The pressure switch 130 is configured to provide a pressure indicationto the furnace control system 139 indicative of the pressure within thecombustion chamber 102. The enclosed space (e.g., the combustion chamber102, the inlet 124, etc.) whose pressure the pressure switch 130 ismeasuring is sometimes referred to herein as a conduit. The pressureswitch 130 includes an open/close switch that is opened when a detectedpressure is below a threshold pressure limit (also referred to as apredetermined pressure or a predetermined threshold) and closed when adetected pressure is above the threshold pressure limit. The pressuretransducer 129 includes an analog and/or digital sensor configured tooutput an analog and/or digital signal indicative of an actual orrelative pressure to the furnace control system 139. In the illustratedembodiment, the pressure switch 130 and the pressure transducer 129 arepositioned proximate the air inlet 124, and configured to detect thepressure of fresh air being supplied to the combustion chamber 102. Inother suitable embodiments, the pressure switch 130 and the pressuretransducer 129 may be positioned at any suitable location within thefurnace system 100 that allows the furnace system to function asdescribed herein including, for example and without limitation, withinthe combustion chamber 102 and within the blower inlet 122.

The temperature sensor 132 is configured to provide a temperatureindication to the furnace control system 139 indicative of a temperatureT2 within the furnace system 100. In the example embodiment, thetemperature sensor 132 includes an open/close switch that is opened whena detected temperature is above a threshold temperature limit and closedwhen a detected temperature is below the threshold pressure limit. Inother suitable embodiments, the temperature sensor 132 includes ananalog and/or digital sensor configured to output an analog and/ordigital signal indicative of an actual or relative temperature to thefurnace control system 139. In the illustrated embodiment, thetemperature sensor 132 is positioned proximate the heat exchanger 104,and is configured to detect a high temperature condition within the heatexchanger 104. That is, the temperature sensor 132 is configured tocommunicate with furnace control system 139 to indicate the presence ofa high temperature condition (e.g., a detected temperature above athreshold temperature limit) within the heat exchanger 104.

The flame rollout detector 134 is configured to detect a flame rolloutcondition within the furnace system 100, and communicate with thefurnace control system 139 to indicate that a flame rollout conditionhas been detected. The term “flame rollout condition” refers to acondition in which the combustion of the air/fuel mixture occurs outsideof the normal combustion area within the combustion chamber 102. Forexample, if the exhaust outlet 126 is impeded during operation, flamesthat are normally confined to an area immediately adjacent the burnerassembly 108 may spread to other areas of the furnace system 100, suchas outside the combustion chamber 102, creating a risk of damagingcomponents of the furnace system 100. Flame rollout detector 134 isconfigured to detect a flame rollout condition to prevent abnormaloperation of furnace system 100 and potential damage to components ofthe furnace system 100. The flame rollout detector 134 may include anysuitable detectors and/or sensors that enable the flame rollout detector134 to function as described herein including, for example and withoutlimitation, temperature sensors, pressure transducers, and opticaldetectors. In the example embodiment, the flame rollout detector 134includes an open/close switch that is opened when a flame rolloutcondition is detected, and closed when the flame rollout condition is nolonger detected. In other suitable embodiments, the open/close switchmay only be closed following the detection of a flame rollout conditionwith human intervention (e.g., by resetting the furnace control system139).

The flame sensor 136 is configured to detect the presence of a flame atthe burner assembly 108, and communicate with the furnace control system139 to indicate the presence or absence of a flame. The flame sensor 136may include any suitable sensor and/or detector for detecting thepresence of a flame including, for example and without limitation,thermo-electric devices (e.g., thermopiles), and optical flamedetectors.

Components of the furnace system 100, such as the main burner valve 116,the ignition device 112, the inducer blower 120, the pressure switch130, the temperature sensor 132, the flame rollout detector 134, and theflame sensor 136, may be electrically connected to the furnace controlsystem 139 by one or more wiring harnesses. In one suitable embodiment,for example, the main burner valve 116, the pressure switch 130, thetemperature sensor 132, the flame rollout detector 134, and the flamesensor 136 are each electrically connected to the furnace control system139 by a primary or main wiring harness, and the ignition device 112 andthe inducer blower 120 are each electrically connected to the furnacecontrol system 139 by a secondary wiring harness. A wiring harness is anassembly of cables or wires bound or secured together by suitable meansincluding, for example and without limitation, straps, cable ties, cablelacing, sleeves, electrical tape, conduit, and combinations thereof. Thewiring harnesses used to connect components of the furnace system 100 tothe furnace control system 139 may include a harness connector adaptedto mate with a complementary harness connector mounted on the furnacecontrol system 139, described in more detail below. In one suitableembodiment, for example, a wiring harness of the furnace system 100includes a male harness connector adapted to mate with a female harnessconnector mounted on the furnace control system 139.

In operation, the thermostat 128 transmits a call for heat to thefurnace control system 139 (e.g., in the form of an electrical signal)when a detected temperature within the temperature controlledenvironment falls below a pre-determined temperature limit. Uponreceiving a call for heat, the furnace control system 139 checks theenvironmental and operating conditions of the furnace system 100 usingone or more of the pressure switch 130, the temperature sensor 132, theflame rollout detector 134, and the flame sensor 136 to ensure thetemperature, pressure, and/or other conditions of the furnace system 100are within predetermined limits. In the example embodiment, the furnacecontrol system 139 outputs a signal to each of the temperature sensor132 and the flame rollout detector 134 to confirm that the open/closeswitch of each of the sensors is in the closed position.

Once the environmental and/or operational conditions check is completed,the furnace control system 139 transmits a signal to the inducer blower120 to energize the inducer blower 120. The furnace control system 139may check the pressure within the furnace system 100 using the pressureswitch 130 to ensure an adequate supply of fresh (i.e., uncombusted) airis being supplied into the combustion chamber 102. In the exampleembodiment, the furnace control system 139 outputs a signal to thepressure switch 130 to confirm that the open/close switch of thepressure switch 130 is in the closed position.

The furnace control system 139 then outputs a signal to the main burnervalve 116 to open the main burner valve 116 and enable the supply offuel gas to the burner assembly 108. Before, during, or after openingthe main burner valve 116, the furnace control system 139 outputs asignal to the ignition device 112 to energize the ignition device 112and ignite the air/fuel mixture within the combustion chamber 102. Wherethe ignition device 112 is a hot surface ignitor, such as in the exampleembodiment, the furnace control system 139 may energize the ignitiondevice 112 prior to energizing the main burner valve 116 to allow theignition device 112 sufficient time to heat up to a temperaturesufficient to initiate combustion. Where the ignition device 112 is anintermittent pilot, the furnace control system 139 energizes the pilotburner valve (not shown) and ignites the intermittent pilot prior toenergizing the main burner valve 116.

The furnace control system 139 may then check whether flame initiationwas successful via the flame sensor 136. For example, the flame sensor136 may output a signal to the furnace control system 139 indicating thepresence of a flame in the combustion chamber 102. If no flame isdetected by flame sensor 136, the furnace control system 139 mayde-energize one or more of the main burner valve 116, the ignitiondevice 112, and the inducer blower 120, and reattempt to initiatecombustion within the combustion chamber 102. If the flame sensor 136detects the presence of a flame, the furnace control system 139energizes the air circulator 106 to circulate air across the heatexchanger 104 and into the temperature controlled environment via outlet138.

When the call for heat has been satisfied (i.e., when the detectedtemperature in the temperature controlled environment is equal to orgreater than a pre-determined temperature limit), the thermostat 128outputs a signal to the furnace control system 139 to indicate the callfor heat has been satisfied. The furnace control system 139 thende-energizes the main burner valve 116, the inducer blower 120, theignition device 112, and the air circulator 106. The furnace controlsystem 139 may maintain the inducer blower 120 and/or the air circulator106 in an energized state for a preset delay period after receiving thesignal to terminate the heat cycle.

In order to ensure that the pressure transducer 129 is functioningproperly (i.e., that it is reliable), the furnace control system 139executes a pressure transducer self-check. The processor 141 isconfigured to perform the algorithm, such as by instructions stored inthe memory 143.

A first implementation of the pressure transducer self-check utilizesboth the pressure transducer 129 and the pressure switch 130. As notedabove, pressure switches are established and reliable technology in HVACsystems. Thus, the first implementation determines the status of thepressure transducer 129 at least in part based on comparison with thepressure switch 130.

Specifically, the processor 141 of the furnace control system 139receive pressure signals output by the pressure transducer 129 andreceives signals indicating whether the pressure switch 130 is in afirst state or a second state. The pressure switch 130 is in the firststate (e.g., closed) when the sensed pressure is below a predeterminedpressure and it switches to the second state (e.g., open) when thesensed pressure reaches or exceeds the predetermined pressure. In thisembodiment, the pressure being sensed is a negative pressure, and as thenegative pressure exceeds a predetermined negative pressure the pressureswitch closes. Oher embodiments may sense a positive pressure, in whichcase as the positive pressure exceeds a predetermined positive pressure,the pressure switch closes. In both positive and negative pressureembodiments, the pressure switch switches to the second state when theabsolute value of the pressure reaches or exceeds a predeterminedpressure. For conciseness and clarity, the embodiments will be describedherein with reference merely to pressure and exceeding a predeterminedpressure without distinguishing between negative and positive pressure,and without repeatedly identifying the pressure as the absolute value ofthe pressure. The processor 141 controls the motor of the draft inducer120 in response to a call for heat and determines a first status of thepressure transducer 129 based at least in part on the received pressuresignals from the pressure transducer 129 and the signals indicatingwhether the pressure switch 130 is in the first state or the secondstate.

Because the pressure transducer 129 and the pressure switch 130 are bothpositioned to be responsive to the same pressure, when the pressureswitch 130 switches from the first state to the second state at thepredetermined pressure, the pressure transducer 129 should measure apressure approximately equal to the predetermined pressure. In otherembodiments, the pressure transducer 129 and the pressure switch 130 arenot positioned to be responsive to the same pressure, but are positionedto be responsive to related pressures, and a correlation between therelated pressures is calculated and used to determine the pressure thatshould be sensed by the pressure transducer 129 when the pressure switch130 changes state. The processor 141 determines the status of thepressure transducer 129 as reliable if the signals from the pressuretransducer 129 indicate a pressure equal to or within a predeterminedrange (above or below) the predetermined pressure of the pressure switch130 at the time when the pressure switch changed from the first state tothe second state. For example, the status may be reliable when themeasured pressure is within 1%, 5%, 10%, 20%, etc. of the predeterminedpressure of the pressure switch 130. Alternatively, the range may begiven as a range of specific pressures. Further, there may be two ormore ranges that are used to determine three possible statuses (e.g.,reliable, questionable/needs repair, unreliable) of the pressuretransducer. For example, a measurement within 5% of the predeterminedpressure may indicate a reliable pressure transducer 129, while ameasurement between 5% and 10% indicates a pressure transducer 129 thathas questionable reliability or possibly needs repair/replacement.Finally, a measurement more than 10% (in this example) away from thepredetermined pressure may indicate an unreliable pressure transducer129.

If the first status indicates that the pressure transducer is notunreliable, the processor 141 continues to operate the draft inducer120. If the status indicates a questionable pressure transducer 129 (inembodiments using such additional ranges), the processor 141 may outputan alert or warning to a user of the system. The alert may be a humancognizable alert, such as a visual or audible alert (e.g., displayed onthe user's thermostat), or may be an electronic alert, such as a messagesent to a remote computing device. When the first status indicates thatthe pressure transducer is unreliable, the processor 141 stops operatingthe draft inducer 120. The processor 141 will also generate an alert inthis case, to notify the user that the system has a fault and will notoperate.

In some embodiments, after determining the first status, the processor141 controls the motor of the draft inducer 120 to decrease the speed ofthe motor until the pressure switch 130 switches back from the secondstate to the first state. The processor 141 then determines a secondpressure in the conduit from the signals output by the pressuretransducer 129 when the pressure switch switches from the second stateto the first state. The processor 141 compares the second pressure tothe predetermined pressure, and determines a second status of thepressure transducer 129 based at least in part on the comparison of thesecond pressure to the predetermined pressure. In some embodiments, thepredetermined pressure when switching from the first state to the secondstate is different than when switching from the second state to thefirst state. In such embodiments, the pressure transducer 129 must passboth the first and second statuses (i.e., both comparisons must indicatethat the transducer is not unreliable) to be considered reliable. Inother embodiments, the predetermined pressure is the same in bothdirections. In such embodiments, the first and second pressures may beaveraged and compared to the predetermined pressure to determine thestatus, or the pressure transducer 129 may need to separately pass boththe first and second statuses. In some embodiments, a status is notdetermined until the pressure switch has switched state in bothdirections and both pressure transducer pressures have been acquired(e.g., there is only a first status based on the first and secondpressure and the predetermined pressure).

After determining the second status, the processor 141 controls thedraft inducer 120 motor to increase the speed of the motor at leastuntil the pressure switch 130 again switches from the first state to thesecond state if the second status does not indicate that the pressuretransducer 129 is unreliable. If the second status indicates that thepressure transducer 129 is unreliable, the processor stops the motor. Insome embodiments, a third comparison similar to the first comparisonabove is performed when the pressure switch again switches from thefirst state to the second state. In other embodiments, there is no thirdcomparison, and the processor continues normal operation if the firstand/or second statuses indicate the pressure transducer 129 is notunreliable.

A second implementation of the pressure transducer self-check does notutilize the pressure switch 130, and may be used in systems with orwithout a pressure switch 130. In an example of the secondimplementation, the pressure measured by the pressure transducer 129 ischecked three different times: before the inducer starts operating,after the inducer has started, and after the inducer speed has reached adesired pressure setpoint. Other embodiments may use only one or two ofthe three checks.

In this implementation, the processor 141 checks the pressure readingfrom the pressure transducer 129 without the draft inducer 120 on. Thiscan be at any time before the draft inducer 120 is turned on toestablish a reading before any pressure is developed by the motor.Generally, this check is performed right before the draft inducer 120 isturned on, such as upon receipt of a call for heat. The ambient pressuremeasured by the pressure transducer 129 without the draft inducer 120 onshould be a value that is above some lower level and below some upperlevel. This will typically be a value within a range of pressures aroundzero (ambient pressure), depending on the particular transducer used.Here the first status can be determined as one of two or threeconditions: reliable/unreliable or reliable/questionable/unreliable. Ina three condition system, the pressure transducer 129 is determined tobe unreliable if the measured pressure is below a low bad threshold orabove a high bad threshold. Reliable would be above a low good thresholdthat is above the low bad threshold and below a high good threshold thatis below the high bad threshold. Questionable would be pressure readingin the band between the low bad threshold and the low good threshold, orabove the high good threshold and below the high bad threshold. In a twocondition system, there is only one upper threshold and one lowerthreshold (also referred to as a range around an expected pressure). Ifthe pressure is between the upper and lower thresholds, the pressuretransducer 129 is reliable, and if the pressure is above the upperthreshold or below the lower threshold, the pressure transducer isunreliable. In either system, if the sensed pressure is in theunreliable range, the processor 141 reports an error and does notproceed with a heat call. If it is in the questionable range, theprocessor continues with the heat call and issues an alert or a warningas discussed in the first implementation. In some embodiments, theprocessor 141 operates the system at a reduced capacity when the statusindicates that the pressure transducer 129 is questionable. If thestatus indicates that the pressure transducer 129 is reliable, theprocessor 141 operates the system as normal.

Blowing wind may affect the pressure being measured by the pressuretransducer 129. Thus, the questionable range may be set to account forexpected variations on pressure due to expected amounts of wind.However, excessive wind may push the pressure readings into theunreliable range. Thus, in some embodiments, when checking the pressurewithout the draft inducer 120 on, the processor 141 will initially runthe inducer 120 even if the sensed pressure is in the unreliable rangein order to determine if the pressure transducer 129 responds asexpected. If wind has affected the sensed pressure, running the inducerwill cause the sensed pressure to change in the expected direction. Ifthe processor 141 detects a change in the signal from the pressuretransducer 129 in the expected direction when the draft inducer 120begins to run, the processor 141 operates the system as normal. If,however, the signal from the pressure transducer 129 does not begin tomove in the expected direction shortly after the draft inducer 120begins to run, the processor 141 determines that the pressure transduceris unreliable, reports an error, stops running the inducer, and does notproceed with a heat call. Alternatively, the processor 141 may run thedraft inducer 120 until the second check is performed.

If the pressure transducer 129 was determined not to be unreliable(i.e., it is reliable or questionable), the processor 141 continuesresponding to the call for heat and operates the draft inducer 120. ASthe draft inducer 120 speeds up and the pressure builds, but beforereaching the desired setpoint, the processor 141 performs the secondcheck. Specifically, the processor 141 check the slope of the pressuresignal verses the draft inducer 120 speed. There should be a positiveslope in the pressure signal that is above a minimum and below a maximumslope for the expected pressure rise versus the speed. This speed can bebased on a commanded or expected speed based on the signals sent to thedraft inducer, or it can be an actual sensed speed of the draft inducer120 motor. As the speed in increased and the pressure increases, thereis a pressure range within a pressure from a properly functioningpressure transducer and inducer motor should appear. This range canagain be divided into two or three groups: reliable/unreliable orreliable/questionable/unreliable. In a three condition system, thepressure transducer 129 is determined to be unreliable if the measuredpressure is below a low bad threshold or above a high bad threshold.Reliable would be above a low good threshold that is above the low badthreshold and below a high good threshold that is below the high badthreshold. Questionable would be pressure reading in the band betweenthe low bad threshold and the low good threshold, or above the high goodthreshold and below the high bad threshold. In a two condition system,there is only one upper threshold and one lower threshold (also referredto as a range around an expected pressure). If the pressure is betweenthe upper and lower thresholds, the pressure transducer 129 is reliable,and if the pressure is above the upper threshold or below the lowerthreshold, the pressure transducer is unreliable. In either system, ifthe sensed pressure is in the unreliable range, the processor 141reports an error, stops the draft inducer 120, and does not proceed witha heat call. If it is in the questionable range, the processor continueswith the heat call and issues an alert or a warning as discussed in thefirst implementation. In some embodiments, the processor 141 operatesthe system at a reduced capacity when the status indicates that thepressure transducer 129 is questionable. If the status indicates thatthe pressure transducer 129 is reliable, the processor 141 operates thesystem as normal.

The final check compares the value of the pressure sensed by thepressure transducer 129 to the expected pressure at the current inducerspeed after reaching the desired pressure setpoint. As with the firstand second checks, there can be two or three possible statuses:reliable/unreliable or reliable/questionable/unreliable. In a threecondition system, the pressure transducer 129 is determined to beunreliable if the measured pressure is below a low bad threshold orabove a high bad threshold. Reliable would be above a low good thresholdthat is above the low bad threshold and below a high good threshold thatis below the high bad threshold. Questionable would be pressure readingin the band between the low bad threshold and the low good threshold, orabove the high good threshold and below the high bad threshold. In a twocondition system, there is only one upper threshold and one lowerthreshold (also referred to as a range around an expected pressure). Ifthe pressure is between the upper and lower thresholds, the pressuretransducer 129 is reliable, and if the pressure is above the upperthreshold or below the lower threshold, the pressure transducer isunreliable. In either system, if the sensed pressure is in theunreliable range, the processor 141 reports an error, stops the draftinducer 120, and does not proceed with a heat call. In otherembodiments, the processor may perform an additional check before makinga final determination the pressure transducer is in the unreliablerange. Alternatively, the processor may treat the sensed pressure as ifit were in the questionable range if the first two checks (beforerunning the inducer and before reaching the desired setpoint) indicatedthat the pressure transducer is reliable. If it is in the questionablerange, the processor continues with the heat call and issues an alert ora warning as discussed in the first implementation. In some embodiments,the processor 141 operates the system at a reduced capacity when thestatus indicates that the pressure transducer 129 is questionable. Ifthe status indicates that the pressure transducer 129 is reliable, theprocessor 141 operates the system as normal.

The various embodiments described above may be separated and combined invarious forms. For example, systems using the three checks of thepressure transducer may also check the pressure transducer against thepressure switch. Other embodiments may perform less than all threechecks of the pressure transducer, such as only performing the firstcheck, the second check, or the third check, or only performing two ofthe first, second, and third checks. Again, these one or two checks mayalso be combined with checking the pressure transducer against thepressure switch.

Example embodiments of gas-powered furnace systems and furnacecontrollers are described above in detail. The system and controller arenot limited to the specific embodiments described herein, but rather,components of the system and controller may be used independently andseparately from other components described herein.

When introducing elements of the present disclosure or the embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising,”“including,” “containing” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements. The use of terms indicating a particular orientation (e.g.,“top”, “bottom”, “side”, etc.) is for convenience of description anddoes not require any particular orientation of the item described.

As various changes could be made in the above constructions and methodswithout departing from the scope of the disclosure, it is intended thatall matter contained in the above description and shown in theaccompanying drawing(s) shall be interpreted as illustrative and not ina limiting sense.

What is claimed is:
 1. A gas furnace system comprising: a draft inducerincluding a motor, the draft inducer in fluid communication with aconduit; a pressure transducer positioned to sense a pressure within theconduit and output signals proportional to the sensed pressure; apressure switch connected to the controller and positioned to sense thepressure within the conduit, the pressure switch having a first stateand a second state, and configured to be in the first state when thesensed pressure is below a predetermined pressure and to switch to thesecond state when the sensed pressure reaches or exceeds thepredetermined pressure; and a controller connected to the draft inducer,the pressure transducer, and the pressure switch, the controllercomprising a processor programmed to: receive pressure signals output bythe pressure transducer; receive signals indicating whether the pressureswitch is in the first state or the second state; control the motor ofthe draft inducer in response to a call for heat; and determine a firststatus of the pressure transducer based at least in part on the receivedpressure signals from the pressure transducer and the signals indicatingwhether the pressure switch is in the first state or the second state.2. The gas furnace system of claim 1, wherein the processor isprogrammed to: continue operating the motor of the draft inducer whenthe first status of the pressure transducer does not indicate that thepressure transducer is unreliable; and stop operation of the motor ofthe draft inducer when the first status of the pressure inducerindicates that the pressure transducer is unreliable.
 3. The gas furnacesystem of claim 2, wherein the processor is programmed to: determinewhen the pressure switch switches from the first state to the secondstate; determine a first pressure from the signals received from thepressure transducer when the processor determines that the pressureswitch switches from the first state to the second state; compare thefirst pressure to the predetermined pressure; and determine the firststatus of the pressure transducer based at least in part on thecomparison of the first pressure to the predetermined pressure.
 4. Thegas furnace system of claim 3, wherein the processor is programmed to:determine the first status of the pressure transducer as unreliable whenthe first pressure is outside a predetermined range from thepredetermined pressure of the pressure switch; and determine the firststatus of the pressure transducer as not unreliable when the firstpressure is within the predetermined range from the predeterminedpressure of the pressure switch.
 5. The gas furnace system of claim 3,wherein the processor is programmed to: control the motor of the draftinducer after determining the first pressure to decrease the speed ofthe motor until the pressure switch switches from the second state tothe first state; determine a second pressure in the conduit from thesignals output by the pressure transducer when the pressure switchswitches from the second state to the first state; compare the secondpressure to the predetermined pressure; and determine a second status ofthe pressure transducer based at least in part on the comparison of thesecond pressure to the predetermined pressure.
 6. The gas furnace systemof claim 5, wherein the processor is programmed to: control the motor toincrease the speed of the motor at least until the pressure switch againswitches from the first state to the second state when the second statusdoes not indicate that the pressure transducer is unreliable; and stopthe motor when the second status indicates that the pressure transduceris unreliable.
 7. The gas furnace system of claim 3, wherein theprocessor is programmed to: control the motor of the draft inducer afterdetermining the first pressure to decrease the speed of the motor untilthe pressure switch switches from the second state to the first state;determine a second pressure in the conduit from the signals output bythe pressure transducer when the pressure switch switches from thesecond state to the first state; compare the second pressure to thepredetermined pressure; and determine the first status of the pressuretransducer based at least in part on the comparison of the secondpressure to the predetermined pressure and the comparison of the firstpressure to the predetermined pressure.
 8. A controller for a gasfurnace system including a draft inducer having a motor, a pressuretransducer positioned to sense a pressure within a conduit and outputsignals proportional to the sensed pressure, and a pressure switchpositioned to sense the pressure within the conduit, the pressure switchhaving a first state and a second state, and configured to be in thefirst state when the sensed pressure is below a predetermined pressureand to switch to the second state when the sensed pressure reaches orexceeds the predetermined pressure, the controller comprising aprocessor programmed to: receive pressure signals output by the pressuretransducer; receive signals indicating whether the pressure switch is inthe first state or the second state; control the motor of the draftinducer in response to a call for heat; and determine a first status ofthe pressure transducer based at least in part on the received pressuresignals from the pressure transducer and the signals indicating whetherthe pressure switch is in the first state or the second state.
 9. Thecontroller of claim 8, wherein the processor is programmed to: continueoperating the motor of the draft inducer when the first status of thepressure transducer does not indicate that the pressure transducer isunreliable; and stop operation of the motor of the draft inducer whenthe first status of the pressure inducer indicates that the pressuretransducer is unreliable.
 10. The controller of claim 9, wherein theprocessor is programmed to: determine when the pressure switch switchesfrom the first state to the second state; determine a first pressurefrom the signals received from the pressure transducer when theprocessor determines that the pressure switch switches from the firststate to the second state; compare the first pressure to thepredetermined pressure; and determine the first status of the pressuretransducer based at least in part on the comparison of the firstpressure to the predetermined pressure.
 11. The controller of claim 10,wherein the processor is programmed to: determine the first status ofthe pressure transducer as unreliable when the first pressure is outsidea predetermined range from the predetermined pressure of the pressureswitch; and determine the first status of the pressure transducer as notunreliable when the first pressure is within the predetermined rangefrom the predetermined pressure of the pressure switch.
 12. Thecontroller of claim 10, wherein the processor is programmed to: controlthe motor of the draft inducer after determining the first pressure todecrease the speed of the motor until the pressure switch switches fromthe second state to the first state; determine a second pressure in theconduit from the signals output by the pressure transducer when thepressure switch switches from the second state to the first state;compare the second pressure to the predetermined pressure; and determinea second status of the pressure transducer based at least in part on thecomparison of the second pressure to the predetermined pressure.
 13. Thecontroller of claim 12, wherein the processor is programmed to: controlthe motor to increase the speed of the motor at least until the pressureswitch again switches from the first state to the second state when thesecond status does not indicate that the pressure transducer isunreliable; and stop the motor when the second status indicates that thepressure transducer is unreliable.
 14. The controller of claim 10,wherein the processor is programmed to: control the motor of the draftinducer after determining the first pressure to decrease the speed ofthe motor until the pressure switch switches from the second state tothe first state; determine a second pressure in the conduit from thesignals output by the pressure transducer when the pressure switchswitches from the second state to the first state; compare the secondpressure to the predetermined pressure; and determine the first statusof the pressure transducer based at least in part on the comparison ofthe second pressure to the predetermined pressure and the comparison ofthe first pressure to the predetermined pressure.
 15. A method ofcontrolling a gas furnace system comprising: controlling a motor of adraft inducer coupled to a conduit to increase a speed of the motor froma stopped condition in response to a call for heat; receiving pressuresignals output by a pressure transducer responsive to pressure in theconduit; receiving signals indicating whether a pressure switchresponsive to pressure in the conduit is in a first state or a secondstate; determining a first status of the pressure transducer based atleast in part on the received pressure signals from the pressuretransducer and the signals indicating whether the pressure switch is inthe first state or the second state; continuing to operate the motorwhen the first status does not indicate that the pressure transducer isunreliable; and stopping the motor when the first status indicates thatthe pressure transducer is unreliable.
 16. The method of claim 15,further comprising: determining when the pressure switch switches fromthe first state to the second state; determining a first pressure fromthe signals received from the pressure transducer when the processordetermines that the pressure switch switches from the first state to thesecond state; comparing the first pressure to the predeterminedpressure; and determining the first status of the pressure transducerbased at least in part on the comparison of the first pressure to thepredetermined pressure.
 17. The method of claim 16, further comprising:determining the first status of the pressure transducer as unreliablewhen the first pressure is outside a predetermined range from thepredetermined pressure of the pressure switch; and determining the firststatus of the pressure transducer as not unreliable when the firstpressure is within the predetermined range from the predeterminedpressure of the pressure switch.
 18. The method of claim 16, furthercomprising: controlling the motor of the draft inducer after determiningthe first pressure to decrease the speed of the motor until the pressureswitch switches from the second state to the first state; determining asecond pressure in the conduit from the signals output by the pressuretransducer when the pressure switch switches from the second state tothe first state; comparing the second pressure to the predeterminedpressure; and determining a second status of the pressure transducerbased at least in part on the comparison of the second pressure to thepredetermined pressure.
 19. The method of claim 18, further comprising:controlling the motor to increase the speed of the motor at least untilthe pressure switch again switches from the first state to the secondstate when the second status does not indicate that the pressuretransducer is unreliable; and stopping the motor when the second statusindicates that the pressure transducer is unreliable.
 20. The method ofclaim 16, further comprising: controlling the motor of the draft inducerafter determining the first pressure to decrease the speed of the motoruntil the pressure switch switches from the second state to the firststate; determining a second pressure in the conduit from the signalsoutput by the pressure transducer when the pressure switch switches fromthe second state to the first state; comparing the second pressure tothe predetermined pressure; and determining the first status of thepressure transducer based at least in part on the comparison of thesecond pressure to the predetermined pressure and the comparison of thefirst pressure to the predetermined pressure.